As I recall, the two Pauls had troubles warming their fuel to a temp where it produced the expected thrust. By the time the ballon reaches the desired altitude, I expect the fuel onboard to be very cold, which could be a problem.

I helped Unreasonable Rocket in their LLC effort as team member, and, yes one of the problems was that one morning the peroxide was cold. But with a vehicle as large as that proposed, it would take a long time to cool.

More important is that rockets with such a low specific impulse cannot reach orbit because the delta V is to be over 6 to 7 times exhaust velocity and the mass ratio to do that is astronomical. For velocity 7 times exhaust velocity the mass ratio would be 1096 for a single stage, and a higher payload to mass would be required for multi stage.

ARCA does not intent to launch anything into orbit using monopropellant. They figured out this some time ago and proposed for HAAS some kind of hybrid engine, based on the same peroxide as oxidant and parfin or bitumen as propellant . However, that strange model shown on their website has no room for the propellant, and what's attached to nozzles looks more like decomposition chambers, too small to accomodate for hundreds of pounds of parrafin or whatever. But that model is definitely something for show ( the sole thing they're excelled so far) and may undergo some changes in the future

I helped Unreasonable Rocket in their LLC effort as team member, and, yes one of the problems was that one morning the peroxide was cold. But with a vehicle as large as that proposed, it would take a long time to cool.

Do you know the concentration of the H2O2 you used and the temperature of that morning?

70% H2O2 freezes at about -40 C and the temperatures between 10 000 m and 14 000 m are below -50 C at this time of the year. The balloon needs at least 1 hour to climb from 10 km to 14 km. There is enough time for a layer of ice to form along the interior walls of Helen rocket.

Also, I am not sure about the reactivity of H2O2 at low temperatures. Nobody expects the hydrogen peroxide in the tanks be above zero at the time the first motor starts.

If still liquid, can hydrogen peroxide be decomposed equally efficient by a catalytic bed no matter of its temperature or simply the efficiency of the reaction and in consequence the ISP of the engine drop dramatically as the H2O2 approaches the solidification point.

You can say that once the decomposition bed gets hot it will heat the cold H2O2 that is fed into it and there will be no problem but the process of rising the temperature will consume energy that otherwise would have been converted into thrust.

85% (I was on his LLC team). 90% decomposed at too high a temperature and it damaged the silver plated screens. There is concern that peroxide from some sources has too much stabilizers, which tends to poison the catalyst.

It is now being produced in US for rocket work, as there are several projects ongoing one of which will be using over a ton/month.

To me, engine design using peroxide looks more difficult that using LOX.

A friend of mine, a pro photog, will arrive Thursday 12th in Constanta for the scheduled Helen launch.I asked him if he can bring along a video camera or a super-zoom optically stabilised photo camera that can shoot video, for the high altitude launch

The launch of the Helen rocket has started -- Romania's first attempt to reach space

The webcast site is not live at the moment but presumably will be as the launch process progresses. The balloon, in particular, will take awhile to reach the proper altitude for the rocket firing. The launch procedure will last about 3 hours.

November 14, 2009 - CONSTANTAARCA has postponed the launch of Helen rocket.The cause was determined by very powerful air currents who twisted the balloon, stopping the inflating process. ARCA team with the help of military divers restored the balloon in correct position and the inflating operation was resumed.This action has had a length over time, in which it was lost the solar radiation intensity required for heating the air inside.We will keep you updated with more news.

The wind in that region has low intensity, as is forecasted for tomorrow, almost zero, that’s something very rare for that sea. The motivation “high winds at altitude” in their press release has too little to do with a balloon that didn’t rise much over the sea level! What do they expect for such a big ball ? That people don’t have a meteorologist or can’t get information about winds in a very limited area?? Did they ever do a rehearsal, using the real balloon starting over the sea waters? I still wonder why don’t they launch from the shore, the air current may send the balloon many kilometers over the sea during ascent. Perhaps they want a bigger cushion for untested, unstabilized rockets that may reach populated regions. Don’t think they really wanted to launch!

85% (I was on his LLC team). 90% decomposed at too high a temperature and it damaged the silver plated screens. There is concern that peroxide from some sources has too much stabilizers, which tends to poison the catalyst.

It is now being produced in US for rocket work, as there are several projects ongoing one of which will be using over a ton/month.

To me, engine design using peroxide looks more difficult that using LOX.